Method of and apparatus for fluidized-bed gasification and melt combustion

ABSTRACT

A combustion method and apparatus in which combustible matter, e.g., waste matter, coal, etc., is gasified to produce a combustible gas containing a sufficiently large amount of combustible component to melt the ash by its own heat. A fluidized-bed furnace ( 2 ) has an approximately circular horizontal cross-sectional configuration. A moving bed ( 9 ), in which a fluidized medium settles and diffuses, is formed in the central portion of the furnace, and a fluidized bed ( 10 ), in which the fluidized medium is actively fluidized, is formed in the peripheral portion in the furnace. The fluidized medium is turned over to the upper part of the moving bed ( 9 ) from the upper part of the fluidized bed ( 10 ), thus circulating through the two beds. Combustible matter ( 11 ) is cast into the upper part of the moving bed ( 9 ) and gasified to form a combustible gas while circulating, together with the fluidized medium. The amount of oxygen supplied to the fluidized-bed furnace ( 2 ) is set so as to be the same contained in an amount of air not higher than 30% of the theoretical amount of combustion air. The temperature of the fluidized bed ( 10 ) is maintained at 450° C. to 650° C. so that the combustible gas produced contains a large amount of combustible component. The combustible gas and fine particles produced in the fluidized-bed furnace ( 2 ) are supplied to a melt combustion furnace where they are burned at high temperature, and the resulting ash is melted.

This is a division of application Ser. No. 08/915,322, filed Aug. 20,1997 now U.S. Pat. No. 5,858,033, which is a division of applicationSer. No. 08/547,126, filed Oct. 24, 1995, now U.S. Pat. No. 5,725,614,which is a division of application Ser. No. 08/401,370, filed Mar. 9,1995, now U.S. Pat. No. 5,620,488.

BACKGROUND OF THE INVENTION Industrially Applicable Field

The present invention relates to a method and an apparatus in whichcombustible matter is gasified in a fluidized-bed furnace, and theresulting combustible gas and fine particles are burned at hightemperature in a melt combustion furnace, and the resulting ash ismelted therein.

In recent years, it has been demanded to reduce the volume of wastes,e.g. municipal refuse, waste plastics, etc., which are generated inlarge amounts, by incineration, and to effectively use heat recoveredfrom such incineration. Since ash resulting from incineration of wastematter generally contains harmful heavy metals, it is necessary to takesome measures, e.g. solidification of the heavy metal component, todispose of the burned ash by reclaiming. To cope with these problems,JP-B2-62-35004 (Japanese Patent Application Post-ExaminationPublication, KOKOKU) proposes a method of and apparatus for burningsolid matter. In the proposed combustion method, a solid material isthermally decomposed in a fluidized-bed pyrolysis furnace, and pyrolysisproducts, that is, a combustible gas and particles, are introduced intoa cyclone combustion furnace, in which the combustible component isburned at high intensity by pressurized air, and the ash is caused tocollide with the wall surface by swirl and thus be melted. The moltenash flows down on the wall surface, and the resulting molten slag dropsfrom a discharge opening into a water chamber where it is solidified.

The method disclosed in JP-B2-62-35004 suffers, however, from thedisadvantage that, since the entire fluidized bed is in an activelyfluidized state, a large amount of unreacted combustible component iscarried to the outside of the furnace with the combustible gas producedin the furnace. Therefore, high gasification efficiency cannot beobtained. Further, gasification materials usable in fluidized-bedfurnaces have heretofore been small coal having a particle diameter inthe range of from 0.5 mm to 3 mm, and finely-crushed waste matter ofseveral millimeters in size. Gasification material that is larger insize than the above will obstruct fluidization; gasification materialthat is smaller in size than the above will be carried to the outside ofthe furnace with the combustible gas as an unreacted combustiblecomponent without being completely gasified. Accordingly, theconventional fluidized-bed furnaces necessitate previously crushing agasification material and making the resulting particles uniform in sizeby using a crusher or the like as a pretreatment which is carried outbefore the gasification material is cast into the furnace. Thus,gasification materials which do not fall within a predetermined particlediameter range cannot be used, and the yield must be sacrificed to someextent.

To solve the above-described problem, JP-A-2-147692 (Japanese PatentApplication Public Disclosure, KOKAI) proposes a fluidized-bedgasification method and fluidized-bed gasification furnace. In thefluidized-bed gasification method disclosed in this publication, thefurnace has a rectangular horizontal cross-sectional configuration, andthe mass velocity of a fluidizing gas jetted out upwardly into thefurnace from the central portion of the furnace bottom is set lower thanthe mass velocity of a fluidizing gas supplied from two side edgeportions of the furnace bottom. The upward stream of the fluidizing gasis turned over to the central portion of the furnace at a position aboveeach side edge portion of the furnace bottom. Thus, a moving bed inwhich a fluidized medium settles is formed in the central portion of thefurnace, and a fluidized bed in which the fluidized medium is activelyfluidized is formed in each side edge portion of the furnace.Combustible matter is supplied to the moving bed. The fluidizing gas iseither a mixture of air and steam, or a mixture of oxygen and steam, andthe fluidized medium is siliceous sand.

However, the method of JP-A-2-147692 has the following disadvantages:

(1) A gasification endothermic reaction and combustion reactionsimultaneously take place in all the moving and fluidized beds.Accordingly, a volatile component, which is readily gasified, is burnedat the same time as it is gasified, whereas, fixed carbon (char) andtar, which are difficult to gasify, are carried, as unreacted matter, tothe outside of the furnace with the combustible gas produced in thefurnace. Thus, no high gasification efficiency cannot be obtained.

(2) In a case where the combustible gas produced in the furnace isburned for use in a steam and gas turbine combined-cycle powergeneration plant, the fluidized-bed furnace must be of the pressurizedtype. In this case, however, since the furnace has a rectangularhorizontal cross-sectional configuration, it is difficult to constructthe furnace in the form of a pressurized furnace. Preferablegasification furnace pressure is determined by the application of thecombustible gas produced. In a case where the gas is used as an ordinarygas for combustion, the furnace pressure may be of the order of severalthousands of mmAq (millimeter of water). However, in a case where thecombustible gas produced is used as a fuel for a gas turbine, thefurnace pressure must be as high as several kgf/cm². When the gas isused as a fuel for high-efficiency gasification combined-cycle powergeneration, a furnace pressure higher than ten-odd kgf/cm² is suitablyused.

In treatment of wastes such as municipal refuse, volumetric reduction byburning combustible refuse still plays an important role. In relation toincineration, there has recently been an increasing demand forenvironmental protection-type refuse treatment techniques, e.g.dioxin-control measures, techniques for making smoke dust harmless,improvements in energy recovery efficiency, etc. The rate ofincineration of municipal refuse in Japan is about 100,000 tons/day, andenergy recovered from such municipal refuse is equivalent to about 4% ofthe electric energy consumed in Japan. At present, the municipal refuseenergy utilization factor is as low as about 10%. However, if the energyutilization factor can be increased, the rate of consumption of fossilfuel decreases correspondingly, so that it is possible to contribute tothe prevention of global warming.

However, the existing incineration system involves the followingproblems:

{circle around (1)} The power generation efficiency cannot be increasedbecause of the problem of corrosion by HCl.

{circle around (2)} Environmental pollution prevention equipment forcontrolling HCl, NO_(x), SO_(x), mercury, dioxins, etc. has becomecomplicated, resulting increased in cost and space requirements.

{circle around (3)} There is an increasing tendency to install burnedash melting equipment on account of tightening of regulations,difficulty in ensuring a site for final disposal, and so forth. For thispurpose, however, additional equipment must be constructed, and a greatdeal of electric power is consumed.

{circle around (4)} Costly equipment is needed to remove dioxins.

{circle around (5)} It is difficult to recover valuable metals.

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

An object of the present invention is to solve the above-describedproblems of the related art and to produce a combustible gas at highefficiency, which contains a large amount of combustible component, fromcombustible matter such as wastes, e.g. municipal refuse, wasteplastics, etc., or combustible matter such as coal.

Another object of the present invention is to provide a method of andapparatus for gasifying combustible matter, which are suitable forrecovery of energy and which can readily produce a high-pressurecombustible gas.

Still another object of the present invention is to provide agasification and melt combustion method and apparatus which are capableof producing a combustible gas containing a large amount of combustiblecomponent and of melting the burned ash by the heat of the combustiblegas produced.

A further object of the present invention is to provide combustible gasof a homogeneous gas containing char and tar with a sufficiently highcalorific value to generate a high temperature of 1,300° C. or higher byits own heat.

A further object of the present invention is to provide a gasificationapparatus in which incombustible matter can be smoothly dischargedtherefrom without any problem.

A further object of the present invention is to provide a gasificationmethod and apparatus which enable valuable metals contained in wastematter to be recovered from a fluidized-bed furnace having a reducingatmosphere without being oxidized.

Means for Solving the Problems

The present invention provides a method of gasifying combustible matterin a fluidized-bed furnace to produce a combustible gas. In the methodof the present invention, the fluidized-bed furnace has an approximatelycircular horizontal cross-sectional configuration. A fluidizing gaswhich is supplied to the fluidized-bed furnace includes a centralfluidizing gas which is supplied as an upward stream from the centralportion of the bottom of the furnace to the inside of the furnace, and aperipheral fluidizing gas which is supplied as an upward stream from theperipheral portion of the furnace bottom to the inside of the furnace.The central fluidizing gas has a lower mass velocity than that of theperipheral fluidizing gas. The upward stream of fluidizing gas andfluidized medium in the upper part of the peripheral portion in thefurnace is turned over or deflected to the central portion of thefurnace by an inclined wall, thereby forming a moving bed, in which afluidized medium (generally, siliceous sand) settles and diffuses, inthe central portion of the furnace, and also forming a fluidized bed, inwhich the fluidized medium is actively fluidized, in the peripheralportion in the furnace, so that combustible matter which is suppliedinto the furnace is gasified to form a combustible gas whilecirculating, together with the fluidized medium, from the lower part ofthe moving bed to the fluidized bed and from the top of the fluidizedbed to the moving bed. The oxygen content of the central fluidizing gasis set not higher than that of the peripheral fluidizing gas, and thetemperature of the fluidized bed is maintained in a range of from 450°C. to 650° C.

In the present invention, the central fluidizing gas is one selectedfrom three gases, i.e. steam, a gaseous mixture of steam and air, andair. The peripheral fluidizing gas is one selected from three gases,i.e. oxygen, a gaseous mixture of oxygen and air, and air.

Accordingly, there are nine ways of combining together the central andperipheral fluidizing gases, as shown in Table 1. An appropriatecombination may be selected according to whether importance is attachedto gasification efficiency or to economy.

In Table 1, combination No. 1 provides the highest gasificationefficiency. However, since the amount of oxygen consumption is large,the cost is high. The gasification efficiency reduces, firstly, as theamount of oxygen consumption decreases, and secondly, as the amount ofsteam consumption decreases. In this case, the cost also reduces. Oxygenusable in the present invention may be high-purity oxygen. It is alsopossible to use low-purity oxygen which is obtained by using an oxygenenrichment membrane. Combination No. 9, which is a combination of airand air, is known as combustion air for conventional incinerators. Inthe present invention, the fluidized-bed furnace has a circularhorizontal cross-sectional configuration, and therefore, the lowerprojected area of an inclined wall which is provided at the upper sideof the peripheral portion in the furnace is larger than the lowerprojected area of an inclined wall which is used in a case where thefluidized-bed furnace has a rectangular horizontal cross-sectional area.Therefore, the flow rate of peripheral fluidizing gas can be increased,and hence the oxygen supply can be increased. Accordingly, thegasification efficiency can be increased.

TABLE 1 Furnace Furnace Central Peripheral No. Portion Portion 1 SteamOxygen 2 ″ Oxygen and Air 3 ″ Air 4 Steam and Air Oxygen 5 ″ Oxygen andAir 6 ″ Air 7 Air Oxygen 8 ″ Oxygen and Air 9 ″ Air

Preferably, in the method of the present invention, the fluidizing gasfurther includes an intermediate fluidizing gas which is supplied to theinside of the furnace from an intermediate portion of the furnace bottombetween the central and peripheral portions of the furnace bottom. Theintermediate fluidizing gas has a mass velocity which is intermediatebetween the mass velocity of the central fluidizing gas and the massvelocity of the peripheral fluidizing gas. The intermediate fluidizinggas is one of two gases, i.e. a gaseous mixture of steam and air, andair. Accordingly, there are 18 ways of combining together the central,intermediate and peripheral fluidizing gases. The oxygen content ispreferably set so as to increase gradually from the central portion tothe peripheral portion of the furnace. There are 15 preferablecombinations of gases as shown in Table 2.

TABLE 2 Furnace Furnace Furnace Central Intermediate Peripheral No.Portion Portion Portion 1 Steam Steam and Air Oxygen 2 ″ ″ Oxygen andAir 3 ″ ″ Air 4 Steam Air Oxygen 5 ″ ″ Oxygen and Air 6 ″ ″ Air 7 Steamand Air Steam and Air Oxygen 8 ″ ″ Oxygen and Air 9 ″ ″ Air 10 Steam andAir Air Oxygen 11 ″ ″ Oxygen and Air 12 ″ ″ Air 13 Air Air Oxygen 14 ″ ″Oxygen and Air 15 ″ ″ Air

An appropriate combination may be selected from among those shown inTable 2 according to whether importance is attached to gasificationefficiency or to economy. In Table 2, combination No. 1 provides thehighest gasification efficiency. However, since the amount of oxygenconsumption is large, the cost is high. The gasification efficiencyreduces, firstly, as the amount of oxygen consumption decreases, andsecondly, as the amount of steam consumption decreases. In this case,the cost also reduces. Oxygen usable in Tables 1 and 2 may behigh-purity oxygen. It is also possible to use low-purity oxygen whichis obtained by using an oxygen enrichment membrane.

When the fluidized-bed furnace is large in size, the intermediatefluidizing gas preferably includes a plurality of fluidizing gases whichare supplied from a plurality of concentrical intermediate portionsprovided between the central and peripheral portions of the furnacebottom. In this case, the oxygen density of the fluidizing gas ispreferably set so that oxygen density is the lowest in the centralportion of the furnace, and it gradually rises toward the peripheralportion of the furnace.

In the method of the present invention, the fluidizing gas that issupplied to the fluidized-bed furnace oxygen contained in an amount ofnot higher than 30% of the theoretical amount of oxygen required forcombustion of combustible matter. Incombustible matter is taken out ofthe fluidized-bed furnace from a peripheral portion of the furnacebottom and classified, and sand obtained by the classification isreturned to the inside of the fluidized-bed furnace. The combustible gasand fine particles produced in the fluidized-bed furnace are burned at ahigh temperature of 1,300° C. or higher in a melt combustion furnace,i.e. a melting furnace, and the ash is melted therein. Exhaust gas fromthe melt combustion furnace is used to drive a gas turbine. The pressurein the fluidized-bed furnace is maintained at a level not lower than orabove atmospheric pressure according to its usage. The combustiblematter, may be waste matter coal, and so forth.

In addition, the present invention provides an apparatus for gasifyingcombustible matter in a fluidized-bed furnace to produce a combustiblegas. The fluidized-bed furnace includes the following constituentelements: a side wall having an approximately circular horizontalcross-sectional configuration; a fluidizing gas dispersing mechanismwhich is disposed in the bottom portion of the furnace; an incombustiblematter outlet which is disposed at the outer periphery of the fluidizinggas dispersing mechanism; a central supply device for supplying afluidizing gas to the inside of the furnace from a central portion ofthe fluidizing gas dispersing mechanism so that the fluidizing gas flowsvertically upward; a peripheral supply device for supplying a fluidizinggas to the inside of the furnace from a peripheral portion of thefluidizing gas dispersing mechanism so that the fluidizing gas flowsvertically upward; an inclined wall for turning over the fluidizing gasand fluidized medium flowing vertically upward to the central portion ofthe furnace at a position above the peripheral supply device; and a freeboard which is disposed above the inclined wall. The central supplydevice supplies a fluidizing gas having a relatively low mass velocityand a relatively low oxygen density. The peripheral supply devicesupplies a fluidizing gas having a relatively high mass velocity and arelatively high oxygen density.

In the apparatus of the present invention, the fluidized-bed furnace mayfurther include an intermediate supply device for supplying a fluidizinggas to the inside of the furnace from a ring-shaped intermediate portionbetween the central and peripheral portions of the fluidizing gasdispersing mechanism so that the fluidizing gas flows vertically upward.The intermediate supply device supplies a fluidizing gas having a massvelocity which is intermediate between the mass velocities of thefluidizing gases supplied by the central and peripheral supply devices,and an oxygen density which is intermediate between the oxygen densitiesof the fluidizing gases supplied by the central and peripheral supplydevices. The peripheral supply device may be a ring-shaped supply box.The fluidized-bed furnace may further include a combustible matter inletwhich is disposed in the upper part of the fluidized-bed furnace. Thecombustible matter inlet may be arranged to drop combustible matter intoa space above the central supply device. The fluidizing gas dispersingmechanism may be formed so that the peripheral portion thereof is lowerthan the central portion thereof.

The incombustible matter outlet may have a ring-shaped portion which isdisposed at the outer periphery of the fluidizing gas dispersingmechanism, and a conical portion which extends downward from thering-shaped portion so as to contract as the distance from thering-shaped portion increases in the downward direction. Theincombustible matter outlet may have a volume regulating discharger, afirst swing valve for sealing, a swing cut-off valve, a second swingvalve for sealing, which are arranged in series.

The apparatus of the present invention may include a melt combustionfurnace, i.e. a melting furnace, in which the combustible gas and fineparticles produced in the fluidized-bed furnace are burned at hightemperature, and the resulting ash is melted. The melt combustionfurnace has a cylindrical primary combustion chamber with anapproximately vertical axis, and a combustible gas inlet for supplyingthe combustible gas and fine particles produced in the fluidized-bedfurnace into the cylindrical primary combustion chamber so that thecombustible gas and fine particles circle about the axis of the primarycombustion chamber. The melt combustion furnace further has a secondarycombustion chamber which is communicated with the cylindrical primarycombustion chamber, and a discharge opening which is provided in thelower part of the secondary combustion chamber so that molten ash can bedischarged from the discharge opening. Exhaust gas from the secondarycombustion chamber of the melt combustion furnace is introduced into awaste heat boiler and an air preheater, thereby recovering waste heat.Exhaust gas from the secondary combustion chamber of the melt combustionfurnace may be used to drive a gas turbine. Exhaust gas may beintroduced into a dust collector where dust is removed before beingreleased into the atmosphere. (Function)

In the method or apparatus of the-present invention, the fluidized-bedfurnace has an approximately circular horizontal cross-sectionalconfiguration, and hence a pressure-resistance furnace structure can beformed. Thus, the pressure in the fluidized-bed furnace can bemaintained at a level not lower than the atmospheric pressure, and it iseasy to raise the pressure of a combustible gas produced fromcombustible matter supplied into the furnace. The high-pressurecombustible gas can be used as a fuel for a gas turbine or boiler-gasturbine combined-cycle power plant which can be run at high efficiency.Therefore, the use of the combustible gas in such a plant makes itpossible to increase the efficiency of energy recovery from combustiblematter.

In the method and apparatus of the present invention, when the purposethereof is to process wastes, the pressure in the fluidized-bed furnaceis preferably maintained at is a level not higher than the atmosphericpressure in order to prevent leakages of an odious smell or a harmfulcombustion gas from the furnace. In such case, the furnace wall can alsoresist well the pressure difference between the inside and the outsideof the furnace wall, since the furnace has an approximately circularhorizontal cross-sectional configuration.

In the present invention, the mass velocity of the central fluidizinggas supplied into the fluidized-bed furnace is set lower than the massvelocity of the peripheral fluidizing gas, and the upward stream offluidizing gas in the upper part of the peripheral portion in thefurnace is turned over to the central portion of the furnace, therebyforming a moving bed, in which a fluidized medium settles and diffuses,in the central portion of the furnace, and also forming a fluidized bed,in which the fluidized medium is actively fluidized, in the peripheralportion in the furnace. Thus, combustible matter which is supplied intothe furnace is gasified to form a combustible gas while circulating,together with the fluidized medium, from the lower part of the movingbed to the fluidized bed and from the top of the fluidized bed to themoving bed. First, mainly a volatile component of combustible matter isgasified by the heat of the fluidized medium (generally, siliceous sand)in the moving bed which moves downward in the center of the furnace.Since the oxygen content of the central fluidizing gas, which forms themoving bed, is relatively low, the combustible gas produced in themoving bed is not practically burned, but it is moved upward to the freeboard, together with the central fluidizing gas, thereby forming ahigh-calorific value combustible gas of good quality.

The combustible matter, i.e. fixed carbon (char) and tar, which has lostits volatile component and been heated in the moving bed, is thencirculated into the fluidized bed and burned by contact with theperipheral fluidizing gas, which has a relatively high oxygen content,in the fluidized bed, thereby changing into a combustion gas and ash,and also generating heat of combustion which maintains the inside of thefurnace at a temperature in the range of from 450° to 650°C. Thefluidized medium is heated by the heat of combustion, and the heatedfluidized medium is turned over to the central portion of the furnace inthe upper part of the peripheral portion of the furnace and then movesdownward in the moving bed, thereby maintaining the temperature in themoving bed at the level required for gasification of the volatilecomponent. Since the whole furnace, in particular central portion of thefurnace, is placed under low-oxygen condition, it is possible to producea combustible gas having a high content of combustible component.Further, metals contained in the combustible matter can be recovered asnon-oxidized valuable matter from the incombustible matter outlet.

In the present invention, the combustible gas and ash, together withother fine particles, which are produced in the fluidized-bed furnace,may be burned in the melt combustion furnace. In such a case, since thecombustible gas contains a large amount of combustible component, thetemperature in the melt combustion furnace can be raised to a highlevel, i.e. 1,300° C. or higher, without the need for a fuel forheating. Thus, the ash can be sufficiently melted in the melt combustionfurnace. The molten ash can be taken out of the melt combustion furnace,and it can be readily solidified by a known method, e.g. water cooling.Accordingly, the volume of ash is considerably reduced, and harmfulmetals contained in the ash are solidified. Therefore, the ash can bechanged into a form capable of reclaiming disposal.

The above and other objects, features and advantages of the presentinvention will become more apparent from the following description ofthe preferred embodiments thereof, taken in conjunction with theaccompanying drawings, in which like reference numerals denote likeelements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic vertical sectional view showing an essential partof a gasification apparatus according to a first embodiment of thepresent invention.

FIG. 2 is a schematic horizontal sectional view of a fluidized-bedfurnace in the gasification apparatus shown in FIG. 1.

FIG. 3 is a schematic vertical sectional view of an essential part of agasification apparatus according to a second embodiment of the presentinvention.

FIG. 4 is a schematic horizontal sectional view of a fluidized-bedfurnace in the gasification apparatus shown in FIG. 3.

FIG. 5 is a schematic vertical sectional view of a gasificationapparatus according to a third embodiment of the present invention.

FIG. 6 is a schematic vertical sectional view of a gasificationapparatus according to a fourth embodiment of the present invention.

FIG. 7 is a flow chart showing one example of a process for refining thegas produced by the gasification apparatus of the present invention.

FIG. 8 is a flow chart showing one example of a process in which ash ismelted.

FIG. 9 is a schematic sectional perspective view of a gasification andmelt combustion apparatus according to a fifth embodiment of the presentinvention.

FIG. 10 shows the arrangement of a fluidized-bed gasification and meltcombustion apparatus according to an embodiment of the present inventionwhich is used in combination with a waste heat boiler and a turbine.

FIG. 11 shows the arrangement of a fluidized-bed gasification and meltcombustion apparatus according to an embodiment of the present inventionwhich is used in combination with a gas cooler.

FIG. 12 shows the arrangement of a fluidized-bed gasification and meltcombustion apparatus according to an embodiment of the present inventionwhich is used in combination with a waste heat boiler and a reactiontower.

FIG. 13 shows the arrangement of a co-generation type fluidized-bedgasification and melt combustion apparatus according to an embodiment ofthe present invention.

FIG. 14 is a flow chart showing the process of a pressurizedgasification combined-cycle power generation type fluidized-bedgasification and melt combustion method according to an embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below in detailwith reference to the accompanying drawings. It should, however, benoted that the present invention is not necessarily limited to theseembodiments. Further, in FIGS. 1 to 14, members which are denoted by thesame reference numerals are the same or corresponding members, andredundant description thereof is omitted.

FIG. 1 is a schematic vertical sectional view showing an essential partof a gasification apparatus 1 according to a first embodiment forcarrying out the gasification method of the present invention. FIG. 2 isa schematic horizontal sectional view of a fluidized-bed furnace in thegasification apparatus shown in FIG. 1. Referring to FIG. 1, thegasification apparatus 1 has a fluidized-bed furnace 2. A fluidizing gasis supplied into the fluidized-bed furnace 2 through a fluidizing gasdispersing mechanism 106 which is disposed in the bottom of the furnace2. The fluidizing gas consists essentially of a central fluidizing gas 7which is supplied from a central portion 4 of the furnace bottom to theinside of the furnace 2 as an upward stream, and a peripheral fluidizinggas 8 which is supplied from a peripheral portion 3 of the furnacebottom to the inside of the furnace 2 as an upward stream.

As shown in Table 1, the central fluidizing gas 7 is one of three gases,i.e. steam, a gaseous mixture of steam and air, and air, and theperipheral fluidizing gas 8 is one of three gases, i.e. oxygen, agaseous mixture of oxygen and air, and air. The oxygen content of thecentral fluidizing gas 7 is set lower than the oxygen content of theperipheral fluidizing gas 8. The amount of oxygen in the entire aquantity of fluidizing gas is set so as to be not higher than 30% of thetheoretical amount of oxygen required for combustion of combustiblematter 11. The inside of the furnace 2 is held under a reducingatmosphere condition.

The mass velocity of the central fluidizing gas 7 is set lower than thatof the peripheral fluidizing gas 8, and the upward stream of fluidizinggas in the upper part of the peripheral portion in the furnace 2 isturned over to the central portion of the furnace 2 by the action of adeflector 6. Thus, a moving bed 9, in which a fluidized medium(generally, siliceous sand) settles and diffuses, is formed in thecentral portion of the furnace 2, and a fluidized bed 10, in which thefluidized medium is actively fluidized, is formed in the peripheralportion of the fluidized-bed furnace 2. The fluidized medium movesupwardly in the fluidized bed 10 in the furnace peripheral portion, asshown by the arrows 118. Then, the fluidized medium is turned over bythe deflector 6 so as to flow into the upper part of the moving bed 9,and moves downwardly in the moving bed 9. Then, the fluidized mediummoves along the gas dispersing mechanism 106 to flow into the lower partof the fluidized bed 10, as shown by the arrows 112. In this way, thefluidized medium circulates through the fluidized and moving beds 10 and9, as shown by the arrows 118 and 112.

Combustible matter 11 is fed into the upper part of the moving bed 9from a combustible matter feed opening 104. The combustible matter 11moves downwardly in the moving bed 9, together with the fluidizedmedium, and while doing so, the combustible matter 11 is heated by theheated fluidized medium, thereby allowing mainly the volatile componentin the combustible matter 11 to be gasified. Since there is no or only asmall amount of oxygen in the moving bed 9, the gas produced, whichconsists mainly of the gasified volatile component, is not burned, butpasses through the moving bed 9, as shown by the arrows 116. Therefore,the moving bed 9 forms a gasification zone G. The produced gas thenmoves to a free board 102 where it moves upwardly, as shown by the arrow120, and is then discharged from a gas outlet 108 as a combustible gas29.

Matter which is not gasified in the moving bed 9, mainly char (fixedcarbon component) and tar 114, moves from the lower part of the movingbed 9 to the lower part of the fluidized bed 10 in the peripheralportion of the furnace 2, together with the fluidized medium, as shownby the arrows 112, and is burned by the peripheral fluidizing gas 8having a relatively high oxygen content and thus partially oxidized. Thefluidized bed 10 forms a combustible matter oxidizing zone S. In thefluidized bed 10, the fluidized medium is heated to a high temperatureby the heat of combustion in the fluidized bed 10. The fluidized mediumheated to a high temperature is turned aside by inclined wall 6 to moveto the moving bed 9, as shown by the arrows 118, thereby serving as aheat source for further gasification. The temperature of the fluidizedbed 10 is maintained in the range of from 450° C. to 650° C., thereby aneffectively controlled combustion reaction to continue.

According to the gasification apparatus 1 shown in FIGS. 1 and 2, thegasification zone G and the oxidation zone S are formed in thefluidized-bed furnace 2, and the fluidized medium is allowed to serve asa heat transfer medium in the two zones G and S. Thus, a high-calorificvalue combustible gas of good quality is produced in the gasificationzone G, and the char and tar 114, which is difficult to gasify, can beefficiently burned in the oxidation zone S. Therefore, gasificationefficiency of the combustible matter can be increased, and a combustiblegas of good quality can be produced.

As shown in FIG. 2, which is a horizontal sectional view of thefluidized-bed furnace 2, the moving bed 9, which forms the gasificationzone G, is circularly formed in the furnace central portion, and thefluidized bed 10, which forms the oxidation zone S, is annularly formedaround the moving bed 9. A ring-shaped incombustible matter dischargeopening 5 is disposed around the periphery of the fluidized bed 10. Byforming the gasification apparatus 1 in a cylindrical configuration, ahigh furnace pressure can be readily borne. It is also possible toprovide a pressure vessel (not shown) separately outside thegasification apparatus 1 in place of the structure in which the furnacepressure is borne by the gasification furnace itself.

FIG. 3 is a schematic vertical sectional view of an essential part of agasification apparatus according to a second embodiment for carrying thegasification method of the present invention. FIG. 4 is a schematichorizontal sectional view of a fluidized-bed furnace in the gasificationapparatus shown in FIG. 3. In the gasification apparatus of the secondembodiment, shown in FIG. 3, a fluidizing gas includes an intermediatefluidizing gas 7′ which is supplied into the fluidized-bed furnace 2from a furnace bottom intermediate portion between the furnace bottomcentral and peripheral portions, in addition to the central fluidizinggas 7 and the peripheral fluidizing gas 8. The mass velocity of theintermediate fluidizing gas 7′ is selected as being intermediate betweenthe mass velocities of the central and peripheral fluidizing gases 7 and8. The intermediate fluidizing gas 7′ is one of three gases, i.e. steam,a gaseous mixture of steam and air, and air.

In the gasification apparatus shown in FIG. 3, the central fluidizinggas 7 is one of three gases, i.e. steam, a gaseous mixture of steam andair, and air, and the peripheral fluidizing gas 8 is one of three gases,i.e. oxygen, a gaseous mixture of oxygen and air, and air, in the sameway as in the case of the gasification apparatus shown in FIG. 1. Theoxygen content of the intermediate fluidizing gas 7′ is selected asbeing intermediate between the oxygen contents of the central andperipheral fluidizing gases 7 and 8. Therefore, there are 15 preferablecombinations of fluidizing gases, as shown in Table 2. It is importantfor each combination that the oxygen content should increase as thedistance from the center of the fluidized-bed furnace 2 increases towardthe peripheral portion thereof. The amount of oxygen in the entireamount of fluidizing gas is set so as to be an amount of air not higherthan 30% of the theoretical amount of oxygen required for combustion ofcombustible matter 11. The inside of the furnace 2 is held under areducing atmosphere condition.

In the gasification apparatus shown in FIG. 3, a moving bed 9, in whicha fluidized medium settles and diffuses, is formed in the centralportion of the furnace 2, and a fluidized bed 10, in which the fluidizedmedium is actively fluidized, is formed in the peripheral portion of thefluidized-bed furnace 2, in the same way as in the case of thegasification apparatus shown in FIG. 1. The fluidized medium circulatesthrough the moving and fluidized beds. 9 and 10, as shown by the arrows118 and 112. An intermediate bed 9′, in which the fluidized mediumdiffuses mainly in the horizontal direction, is formed between themoving bed 9 and fluidized bed 10. The moving bed 9 and the intermediatebed 9′ form a gasification zone G, and the fluidized bed 10 forms anoxidation zone S.

Combustible matter 11, which is cast into the upper part of the movingbed 9, is heated while moving downwardly in the moving bed 9 togetherwith the fluidized medium, thereby enabling the volatile component inthe combustible matter 11 to be gasified. Char and tar, together with apart of the volatile component, which were not gasified in the movingbed 9, move to the intermediate bed 9′ and the fluidized bed 10,together with the fluidized medium, thereby being partially gasified andpartially burned. Matter that is not gasified in the intermediate bed9′, mainly char and tar, moves into the fluidized bed 10 in the furnaceperipheral portion, together with the fluidized medium, and is burned inthe peripheral fluidizing gas 8 having a relatively high oxygen content.The fluidized medium is heated in the fluidized bed 10 and thencirculates to the moving bed 9 where it heats combustible matter in themoving bed 9. The oxygen density in the intermediate bed 9′ is selectedaccording to the type of combustible matter (i.e. whether the volatilecontent is high or the char and tar content is high). That is, it isdecided according to the type of combustible matter whether the oxygendensity should be made low to mainly perform gasification, or the oxygendensity should be made high to mainly perform oxidation combustion.

As shown in FIG. 4, which is a horizontal sectional view of thefluidized-bed furnace 2, the moving bed 9, which forms a gasificationzone, is circularly formed in the central portion of the furnace 2, andthe intermediate bed 9′ is formed from the intermediate fluidizing gas7′ along the outer periphery of the moving bed 9. The fluidized bed 10,which forms an oxidation zone, is annularly formed around theintermediate bed 9′. A ring-shaped incombustible matter dischargeopening 5 is disposed around the periphery of the fluidized bed 10. Byforming the gasification apparatus 1 in a cylindrical configuration, ahigh furnace pressure can be readily borne. The furnace pressure may beborne by the gasification apparatus itself, or by a pressure vesselwhich is separately provided outside the gasification apparatus.

FIG. 5 is a schematic vertical sectional view of a gasificationapparatus according to a third embodiment of the present invention. Inthe gasification apparatus 1 shown in FIG. 5, a gasification material 11which is combustible matter, e.g. refuse, is supplied to a fluidized-bedfurnace 2 by a double damper 12, a compression feeder 13, and a refusefeeder 14. The compression feeder 13 compresses the gasificationmaterial 11 into a plug-like shape, thereby allowing the furnacepressure to be sealed. The refuse compressed in a plug-like shape isdisintegrated by a disintegrator (not shown) and fed into thefluidized-bed furnace 2 by the refuse feeder 14.

In the gasification apparatus shown in FIG. 5, the central fluidizinggas 7 and the peripheral fluidizing gas 8 are supplied in the same wayas in the embodiment shown in FIG. 1. Therefore, gasification andoxidation zones of reducing atmosphere are formed in the fluidized-bedfurnace 2 in the same way as in the embodiment shown in FIG. 1. Thefluidized medium serves as a heat transfer medium in the two zones. Inthe gasification zone, a high-calorific value combustible gas of goodquality is produced; in the oxidation zone, char and tar, which aredifficult to gasify, are efficiently burned. Thus, it is possible toobtain a high gasification efficiency and a combustible gas of goodquality. In the embodiment shown in FIG. 5, a Roots blower 15 isprovided to communicate with both the double damper 12 and the freeboard 102 in the gasification apparatus 1, so that gas leaking out fromthe furnace 2 to the double damper 12 through the compression feeder 13when the compression of refuse is insufficient is returned to thefurnace 2 by the action of the Roots blower 15. Preferably, the Rootsblower 15 sucks an appropriate amount of air and gas from the doubledamper 12 and returns it to the furnace 2 so that the pressure in theupper stage of the double damper 12 is equal to atmospheric pressure.

Further, the gasification apparatus shown in FIG. 5 has an incombustiblematter discharge opening 5, a conical chute 16, a volume regulatingdischarger 17, a first swing valve 18 for sealing, a swing cut-off valve19, a second swing valve 20 for sealing, and a discharger 23 equippedwith a trommel, which are disposed in the mentioned order and operatedas follows:

(1) In a state where the first swing valve 18 for sealing is open, whilethe second swing valve 20 is closed, and the furnace pressure is sealedby the second swing valve 20, the volume regulating discharger 17 isoperated, so that incombustible matter including sand as a fluidizedmedium is discharged from the conical chute 16 to the swing cut-offvalve 19.

(2) When the swing cut-off valve 19 has received a predetermined amountof incombustible matter, the volume regulating discharger 17 is switchedoff, and the first swing valve 18 is closed, so that the furnacepressure is sealed by the first swing valve 18. Further, a dischargevalve 22 is opened, so that the pressure in the swing cut-off valve 19is returned to atmospheric pressure. Next, the second swing valve 20 iscompletely opened, and the swing cut-off valve 19 is opened, therebyallowing incombustible matter to be discharged to the discharger 23.

(3) After the second swing valve 20 has been completely closed, anequalizing valve 21 is opened. After the pressure in the first swingvalve 18 and the pressure in the conical chute 16 have been equalizedwith each other, the first swing valve 18 is opened. Thus, the processreturns to the first step (1).

These steps (1) to (3) are automatically repeated.

The discharger 23, which is equipped with a trommel, is continuouslyrun. Thus, large-sized incombustible matter 27 is discharged to theoutside of the system through the trommel, and sand and small-sizedincombustible matter are transported by a sand circulating elevator 24.After finely-divided incombustible matter 28 has been removed by aclassifier 25, the sand is returned to the gasification apparatus 1through a lock hopper 26. In this incombustible matter dischargingmechanism, the two swing valves 18 and 20 do not receive incombustiblematter but have only a pressure seal function. Accordingly, it ispossible to avoid biting of incombustible matter at the sealing portionsof the first and second swing valves 18 and 20. In a case where thefurnace pressure may be slightly negative, no seal function is required.

FIG. 6 is a schematic vertical sectional view of a gasificationapparatus according to a fourth embodiment of the present invention. Inthe gasification apparatus shown in FIG. 6, the feed of the gasificationmaterial 11 and the furnace pressure sealing operation related theretoare carried out by using a combination of a pair of swing cut-off valves19 and 19′ and a pair of first and second swing valves 18 and 20 in thesame way as in the case of the mechanism for discharging incombustiblematter shown in FIG. 5. The compression feeder 13 used in the embodimentshown FIG. 5 is omitted. In the embodiment shown in FIG. 6, gas leakingout from the furnace to the first swing valve 18 is returned to thefurnace through a discharge valve 22 and a blower (not shown). Further,after the first swing valve 18 has been completely closed, theequalizing valve 21 is opened to equalize the pressure in the swingcut-off valve 19 with the pressure in the furnace.

FIG. 7 is a flow chart showing one example of a process for refining thegas produced by the gasification apparatus of the present invention. Inthe refining process shown in FIG. 7, the gasification apparatus 1 issupplied with the gasification material 11 and the fluidizing gases 7and 8. The combustible gas produced in the gasification apparatus 1 issent to a waste heat boiler 31 where heat is recovered, and the gas thuscooled is then sent to a cyclone separator 32 where solid matter 37 and38 is separated. Thereafter, the combustible gas is scrubbed and cooledin a water scrubbing tower 33, and hydrogen sulfide is removed from thecombustible gas in an alkaline solution scrubbing tower 34. Thereafter,the combustible gas is stored in a gas holder 35. Unreacted char 37 inthe solid matter separated in the cyclone separator 32 is returned tothe gasification apparatus 1, and the remaining solid matter 38 isdischarged to the outside of the system. Large-sized incombustiblematter 27 in the incombustible matter discharged from the gasificationapparatus 1 is discharged to the outside of the system, whereas sand inthe incombustible matter is returned to the gasification apparatus 1, inthe same way as in the embodiment shown in FIG. 5. Waste water from thescrubbing towers 33 and 34 is introduced into a waste water treatmentdevice 36 where it is made harmless.

FIG. 8 is a flow chart showing one example of a process in which thecombustible gas and fine particles produced in the gasificationapparatus 1 are introduced into a melt combustion furnace 41 where theyare burned at high temperature, and the resulting ash is melted. In theprocess shown in FIG. 8, the combustible gas 29 containing a largeamount of combustible component, which has been produced in thegasification apparatus 1, is introduced into the melt combustion furnace41. The melt combustion furnace 41 is also supplied with the gas 8,which is one of three gases, i.e. oxygen, a gaseous mixture of oxygenand air, and air, so that the combustible gas and fine particles areburned at 1,300° C. or higher, and the resulting ash is melted. Inaddition, harmful substances, e.g. dioxins, PCB, etc., are decomposed.The molten ash 44 discharged from the melt combustion furnace 41 iscooled rapidly to form slag, thereby achieving waste volumetricreduction. Combustion exhaust gas generated from the melt combustionfurnace 41 is cooled rapidly in a scrubber 42, thereby preventingresynthesis of dioxins. The exhaust gas cooled rapidly in the scrubber42 is sent to a dust collector 43, e.g. a filter where dust 38 isremoved from the gas. Then, the exhaust gas is discharged into theatmosphere from an exhaust tower 55.

FIG. 9 is a schematic sectional perspective view of a gasification andmelt combustion apparatus according to a fifth embodiment of the presentinvention. Referring to FIG. 9, the gasification apparatus 1 issubstantially the same as that in the embodiment shown FIG. 1. However,the gas outlet 108 is communicated with a combustible gas inlet 142 ofthe melt combustion furnace 41. The melt combustion furnace 41 includesa cylindrical primary combustion chamber 140 having an approximatelyvertical axis, and a secondary combustion chamber 150 which is inclinedhorizontally. Combustible gas 29 and fine particles produced in thefluidized-bed furnace 2 are supplied to the primary combustion chamber140 through the combustible gas inlet 142 so as to circle about the axisof the primary combustion chamber 140.

The upper end of the primary combustion chamber 140 is provided with astarting burner 132 and a plurality of air nozzles 134 which supplycombustion air so that the air circles about the axis of the primarycombustion chamber 140. The secondary combustion chamber 150 iscommunicated with the primary combustion chamber 140 at the lower endthereof. The secondary combustion chamber 150 has a slag separator 160and a discharge opening 152 which is disposed in the lower part of thesecondary combustion chamber 150 so as to be capable of dischargingmolten ash 4, and an exhaust opening 154 which is disposed above thedischarge opening 152. The secondary combustion chamber 150 further hasan assist burner 136 which is disposed in the vicinity of that portionof the secondary combustion chamber 150 at which the chamber 150communicates with the primary combustion chamber 140, and an air nozzle134 for supplying combustion air. The exhaust opening 154 fordischarging an exhaust gas 46 is provided with a radiating plate 162 toreduce the quantity of heat lost through the exhaust opening 154 byradiation.

FIG. 10 shows the arrangement of a fluidized-bed gasification and meltcombustion apparatus according to an embodiment of the present inventionwhich is used in combination with a waste heat boiler and a turbine.Referring to FIG. 10 the gasification apparatus 1 has a conveyor 172 fortransporting large-sized incombustible matter 27 discharged from thedischarger 23, together with finely-divided incombustible matter 28discharged from the classifier 25. An air jacket 185 is disposed aroundthe conical chute 16 which is used to take out incombustible matter fromthe bottom of the fluidized-bed furnace 2. Air in the air jacket 185 isheated by high-temperature sand drawn out of the fluidized-bed furnace2. An auxiliary fuel F is supplied to the primary and secondarycombustion chambers 140 and 150 of the melt combustion furnace 41.

Molten ash 44 discharged from the discharge opening 152 of the meltcombustion furnace 41 is received into a water chamber 178 where it iscooled rapidly, and then discharged as slag 176.

In the arrangement shown in FIG. 10, combustion gas discharged from themelt combustion furnace 41 is discharged into the atmosphere through thewaste heat boiler 31, an economizer 183, an air preheater 186, a dustcollector 43, and an induced draft fan 54. A neutralizer N, e.g. slakedlime (calcium hydroxide), is added to the combustion gas coming out ofthe air preheater 186 before the gas enters the dust collector 43. WaterW is supplied to the economizer 183 where it is preheated, and thenheated in the boiler 31 to form steam. The steam is used to drive asteam turbine ST. Air A is supplied to the air preheater 186 where it isheated, and then further heated in the air jacket 185. The heated air issupplied through an air pipe 184 to the melt combustion furnace 41. Ifnecessary, the heated air is also supplied to the free board 102.

Fine particles 180 and 190 collected in the bottoms of the waste heatboiler 31, the economizer 183 and the air preheater 186 are transportedto the classifier 25 by the sand circulating elevator 24 to removefinely-divided incombustible matter 28 from them, and are then returnedto the fluidized-bed furnace 2. Fly ash 38 separated in the dustcollector 43 contains salts of alkali metals, e.g. Na, K, etc.,volatilized at high temperature, and it is therefore treated withchemicals in a treating device 194.

In the apparatus shown in FIG. 10, combustion in the fluidized-bedfurnace 2 is carried out by low-temperature partial burning method inlow excess air ratio, and the fluidized-bed temperature is maintained inthe range of from 450° C. to 650° C., thereby enabling a high-calorificvalue combustible gas to be produced. Further, since combustion takesplace at a low excess air ratio under a reducing atmosphere condition,iron and aluminum are obtained as unoxidized valuables. Thehigh-calorific value combustible gas and char produced in thefluidized-bed furnace 2 can be burned at high temperature, i.e. 1,300°C. or higher, in the melt combustion furnace 41. Thus, the ash can bemelted, and dioxins can be decomposed.

FIG. 11 shows the arrangement of a fluidized-bed gasification and meltcombustion apparatus according to an embodiment of the present inventionwhich is used in combination with a gas cooler 280. Referring to FIG.11, the gasification apparatus 1, the melt combustion furnace 41, thewater chamber 178, the dust collector 43, the induced draft fan 54,etc., are the same as those in FIG. 10. In the arrangement shown in FIG.11, a gas cooler 280 and an independent air preheater 188 are providedin place of the waste heat boiler. High-temperature combustion exhaustgas from the melt combustion furnace 41 is introduced into the gascooler 280 through a high-temperature duct 278 coated with a thermalinsulator. In the gas cooler 280, the combustion gas is instantaneouslycooled down by spraying with fine water droplets, thereby preventingresynthesis of dioxins. The flow velocity of exhaust gas in thehigh-temperature duct 278 is set at a low level, i.e. 5 m/sec. or lower.A hot-water generator 283 is disposed in the upper part of the gascooler 280. Air heated in the air preheater 188 is supplied to the freeboard 102 in the gasification apparatus 1 and also to the meltcombustion furnace 41.

FIG. 12 shows the arrangement of a fluidized-bed gasification and meltcombustion apparatus according to an embodiment of the present inventionwhich is used in combination with the waste heat boiler 31 and areaction tower 310. In FIG. 12, the gasification apparatus 1, the meltcombustion furnace 41, the water chamber 178, the waste heat boiler 31,the steam turbine ST, the economizer 183, the air preheater 186, thedust collector 43, the induced draft fan 54, etc. are the same as thosein FIG. 10. In the arrangement shown in FIG. 12, reaction tower 310 anda superheater heating combustor 320 are disposed between the waste heatboiler 31 and the economizer 183. In the reaction tower 310, aneutralizer N, e.g. slaked lime slurry, is added to the combustionexhaust gas, thereby removing HCl from the gas. Solid fine particles 312discharged from the reaction tower 310, together with solid fineparticles 180 discharged from the waste heat boiler 31, are sent to theclassifier 25 by the sand circulating elevator 24. In the heatingcombustor 320, combustible gas and an auxiliary fuel F is burned toraise the steam temperature to about 500° C. In the apparatus shown inFIG. 12, the steam has a high temperature and high pressure, and theexcess air ratio is low, and hence the quantity of sensible heat carriedover by the exhaust gas is small. Therefore, the power generationefficiency can be increased to about 30%.

FIG. 13 shows the arrangement of a co-generation type fluidized-bedgasification and melt combustion apparatus according to an embodiment ofthe present invention. In FIG. 13, the gasification apparatus 1, themelt combustion furnace 41, the water chamber 178, the waste heat boiler31, the dust collector 43, the induced draft fan 54, etc. are the sameas those in the apparatus shown in FIG. 10. Referring to FIG. 13, thereaction tower 310 is disposed between the waste heat boiler 31 and thedust collector 43. In the reaction tower 310, a neutralizer N, e.g.slaked lime slurry, is added to the combustion exhaust gas, therebyremoving HCl. Exhaust gas from the reaction tower 310 is suppliedthrough the dust collector 43 to a gas turbine 30 assembly 420 where itis used. In the gas turbine assembly 420, air A is compressed by acompressor C, and the compressed air is supplied to a combustor CC. Inthe combustor CC, a fuel F is burned, and the resulting combustion gas,together with the exhaust gas which is compressed in a compressor 410and supplied to the combustor CC, is used as a working fluid for aturbine T. Exhaust gas from the gas turbine assembly 420 is passedthrough a superheater 430, an economizer 440 and an air preheater 450 inthe mentioned order and then released into the atmosphere by the induceddraft fan 54. Steam generated in the waste heat boiler 31 is heated bythe exhaust gas from the gas turbine assembly 420 in the superheater430, and the heated steam is supplied to the steam turbine ST.

FIG. 14 is a flow chart showing the process of a pressurizedgasification combined-cycle power generation type fluidized-bedgasification and melt combustion method according to an embodiment ofthe present invention. High-temperature and high-pressure combustiblegas 29 produced in the pressurized gasification furnace 1 is introducedinto a waste heat boiler 31′ where it causes steam to be generated, andthe gas itself is cooled. The gas coming out of the waste heat boiler31′ is divided into two, one of which is introduced into the meltcombustion furnace 41, and the other is introduced into a dust collector43′ after a neutralizer N has been added thereto to neutralize HCl. Inthe dust collector 43′, low-melting substances 38′ in the combustiblegas which have solidified because of fall in temperature are separatedfrom the combustible gas and sent to the melt combustion furnace 41where the low-melting substances 38′ are melted. The combustible gaswhich has been ridded of the low-melting substances 38′ is used as afuel gas in the gas turbine assembly GT. Exhaust gas from the gasturbine assembly GT is subjected to heat exchange in a superheater SHand an economizer Eco, and thereafter, it is treated in an exhaust gastreating device 510 and then released into the atmosphere. Exhaust gasfrom the melt combustion furnace 41 is passed through a heat exchangerEX and the dust collector 43 and introduced into the exhaust gastreating device 510. Molten ash 44 discharged from the melt combustionfurnace 41 is cooled rapidly to form slag. Solid matter 38 dischargedfrom the dust collector 43 is treated with chemicals in the treatingdevice 194.

With the process shown in FIG. 14, a gas produced from waste matter isused as a fuel after HCl and solid matter have been removed therefrom.Accordingly, the gas turbine will not be corroded by the gas. Further,since HCl has been removed from the gas, high-temperature steam can begenerated by the gas turbine exhaust gas.

Effects of the Invention

Accordingly, the present invention provides the following advantageouseffects:

(1) In the gasification apparatus of the present invention, heat isdiffused by circulating streams in the fluidized-bed furnace. Therefore,high intensity combustion can be realized, and the furnace can bereduced in size.

(2) In the present invention, the fluidized-bed furnace can maintaincombustion with a relatively small amount of air. Therefore, it ispossible to produce a homogeneous gas containing a large amount ofcombustible component by gently carrying out low-excess air ratio andlow-temperature (450° C. to 650° C.) combustion in the fluidized-bedfurnace and thus minimizing heat generation. Thus, the greater part ofcombustible matter contained in the gas, tar and char can be effectivelyutilized in a melt combustion furnace at the following stage.

(3) In the present invention, even large-sized incombustible matter canbe readily discharged by the action of the circulating streams in thefluidized-bed furnace. In addition, iron and aluminum contained in theincombustible matter can be utilized as unoxidized valuables.

(4) The present invention provides a method or equipment whereby refusetreatment can be made harmless, and a high energy utilization factor canbe attained.

Although the present invention has been described through specificterms, it should be noted here that the described embodiments are notnecessarily exclusive and that various changes and modifications may beimparted thereto without departing from the scope of the invention whichis limited solely by the appended claims.

What is claimed is:
 1. A method of gasifying combustible materialcontaining incombustible matter, said method comprising: providing afluidized bed of fluidized medium within a fluidized-bed reactor bysupplying thereto an oxygen-containing gas as fluidizing gas; creating acirculating flow of said fluidized medium within said reactor by movingsaid fluidized medium upwardly in a first area of said reactor, and bymoving said fluidized medium downwardly in a second area of saidreactor; introducing a supply of said combustible material to beprocessed onto said fluidized bed such that said combustible materialmoves downwardly with said fluidized medium in said second area of saidreactor, thereby gasifying said combustible material to generatecombustible gas and char, and such that said char moves upwardly withsaid fluidized medium in said first area of said reactor and ispartially oxidized to form char particles, said fluidized bed beingmaintained at a temperature in the range of from 450° C. to 650° C., andan amount of oxygen in said oxygen-containing gas being no greater than30% of a theoretical amount of oxygen required for combustion of saidcombustible material; discharging through an outlet said incombustiblematter contained in the supply of combustible material and fluidizedmedium from said reactor, separating the thus discharged fluidizedmedium from said incombustible matter, and returning the thus separatedfluidized medium to said reactor; and discharging said combustible gasand char particles from said fluidized-bed reactor.
 2. A method asclaimed in claim 1, wherein a fluidizing gas in said first area of saidreactor is of a greater mass velocity than a fluidizing gas in saidsecond area of said reactor.
 3. A method as claimed in claim 1, whereinsaid fluidized-bed reactor has an inclined wall for turning over anupward flow of said fluidized medium in a peripheral portion of saidfluidized-bed reactor toward a central portion of said fluidized-bedreactor.
 4. A method as claimed in claim 1, wherein said combustible gasand char particles from said fluidized-bed reactor are supplied to amelt combustion furnace.
 5. A method as claimed in claim 1, wherein saidincombustible matter includes aluminum.
 6. A method for treatingcombustible material, said method comprising: creating a circulatingflow of a fluidized medium within a fluidized-bed reactor by providingan area of a fluidizing gas having a greater mass velocity and an areaof a fluidizing gas having a smaller mass velocity, said fluidizing gasbeing supplied to a bottom portion of said fluidized-bed reactor;supplying combustible material into said fluidized-bed reactor andgasifying said combustible material to produce combustible gas and charparticles in said fluidized-bed reactors said fluidized bed beingmaintained at a temperature in the range of from 450° C. to 650° C.;discharging through an outlet incombustible matter contained in saidcombustible material and said fluidized medium from said fluidized-bedreactor, separating the thus discharged fluidized medium from saidincombustible matter, and returning the thus separated fluidized mediumto said fluidized bed in said fluidized-bed reactor; and dischargingcombustible gas together with said char particles from saidfluidized-bed reactor and introducing said combustible gas together withsaid char particles into a high temperature furnace and combusting saidcombustible gas at a temperature of at least 1300° C. within said hightemperature furnace to melt ash into molten slag.
 7. A method fortreating combustible material, said method comprising: creating afluidized bed of a fluidized medium in a fluidized-bed reactor byproviding an area of a fluidizing gas having a greater mass velocity andan area of a fluidizing gas having a smaller mass velocity, saidfluidizing gas being supplied to a bottom portion of said fluidized-bedreactor; supplying combustible material into said fluidized-bed reactorand gasifying said combustible material to produce combustible gas andchar particles in said fluidized-bed reactor, said fluidized bed beingmaintained at a temperature in the range of from 450° C. to 650° C.; anddischarging said combustible gas and said char from said fluidized-bedreactor and introducing said combustible gas and said char into a hightemperature furnace and combusting said combustible gas and said char ata temperature of at least 1300° C. within said high temperature furnaceto melt ash contained in said char into molten slag.
 8. A method fortreating combustible material, said method comprising: forming a movingbed in which a fluidized medium settles and a fluidized bed in whichsaid fluidized medium is actively fluidized by supplying a fluidizinggas into a fluidized-bed reactor; supplying combustible material intosaid fluidized-bed reactor and gasifying said combustible material insaid fluidized-bed reactor to produce combustible gas and charparticles, said fluidized bed being maintained at a temperature in therange of from 450° C. to 650° C.; discharging through an outletincombustible matter contained in said combustible material and saidfluidized medium from said fluidized-bed reactor while sealing thepressure of said fluidized-bed reactor, separating the thus dischargedfluidized medium from said incombustible matter, and returning the thusseparated fluidized medium to said fluidized bed in said fluidized-bedreactor; and discharging said combustible gas and said char from saidfluidized-bed reactor and introducing said combustible gas and said charinto a high temperature furnace and combusting said combustible gas andsaid char at a temperature of at least 1300° C. within said hightemperature furnace to melt ash contained in said char into molten slag.